This is correct implementation of the List. Thank you guys especially Agent_L who helped me privately.
CORRECT LINKED LIST IMPLEMENTATION
#include <cstdio>
#include <cmath>
#include<iostream>
#include <stdio.h>
#include <string.h>
using namespace std;
class Node{
friend class List;
public:
Node(Node* next, int wrt){
this->next = next;
this->wrt = wrt;
}
Node(const Node& obiekt){
this->wrt = obiekt.wrt;
this->next = obiekt.next;
}
//NIE MA DESTRUKTORA BO NIE ALOKUJE ZADNYCH DANYCH !!!
void show(){
cout<<this->wrt<<endl;
}
private:
Node* next;
int wrt;
};
class List{
public:
List(int wrt){
this->root = new Node(NULL, wrt);
}
List(const List& list)
{
// jesli pusty kopiujemy
if (list.root == NULL)
{
this->root = NULL;
return;
}
//tworzenie nowego korzenia
this->root = new Node(NULL, list.root->wrt);
Node* list_currentNode = list.root;
Node* this_currentNode = this->root;
while (list_currentNode->next != NULL)
{
// tworzenie nastepnika
Node* newNode = new Node(NULL, list_currentNode->next->wrt);
this_currentNode->next = newNode;
this_currentNode = this_currentNode->next;
list_currentNode = list_currentNode->next;
}
}
void add(int wrt){
Node* node = new Node(NULL, wrt);
Node* el = this->root;
while(el->next != NULL){
//el->show();
el = el->next;
}
el->next = node;
}
void remove(int index){
Node* el = this->root;
if(index == 0){
this->root = el->next;
delete el;
}
else{
int i = 0;
while(el != NULL && i < index - 1){
el = el->next;
i++;
}
if(el!=NULL){
Node* toRem = el->next;
Node* newNext = toRem->next;
el->next = newNext;
delete toRem;
}
}
}
void show(){
Node* el = this->root;
while(el != NULL){
el->show();
el = el->next;
}
}
~List(){
Node* currentNode = this->root;
while (currentNode != NULL)
{
Node* nextNode = currentNode->next;
delete currentNode;
currentNode = nextNode;
}
}
private:
Node* root;
};
int main(){
List* l = new List(11);
l->add(22); l->add(33);
l->show();
cout<<endl;
List* lala = new List(*l);
lala->show();
cout<<endl;
lala->add(44);
cout<<"lala before remove"<<endl;
lala->show();
lala->remove(1);
cout<<"l before delete"<<endl;
l->show();
cout<<"lala before delete"<<endl;
lala->show();
delete l;
/* cout<<"l after delete "<<endl;
l->show(); */
cout<<"lala after delete"<<endl;
lala->show();
return 0;
}
I've implemented List and there is a problem. I've destructor in List which doesn't work as it should: please look at main and see "l after delete" it does print l list backwards.
The bigger problem is remove method without delelete inside it works as it should but when I try to uncomment delete el/delete to Rem I get into infinite loop.
Why these lines especially 87 (forget 100) cause the program crashes when I call l->remove(0)?
http://wklej.org/id/761056/ Lines 87 and 100
remove method and List destructor are important
void remove(int index){
Node* el = this->root;
if(index == 0){
this->root = el->next;
// delete el;
}
else{
int i = 0;
while(el != NULL && i < index - 1){
el = el->next;
i++;
}
if(el!=NULL){
Node* toRem = el->next;
Node* newNext = toRem->next;
el->next = newNext;
// delete toRem;
}
}
}
~List(){
Node* currentNode = this->root;
while (currentNode != NULL)
{
Node* nextNode = currentNode->next;
delete currentNode;
currentNode = nextNode;
}
}
Whole code
#include <cstdio>
#include <cmath>
#include<iostream>
#include <stdio.h>
#include <string.h>
using namespace std;
class Node{
friend class List;
public:
Node(Node* next, int wrt){
this->next = next;
this->wrt = wrt;
}
Node(const Node& obiekt){
this->wrt = obiekt.wrt;
this->next = obiekt.next;
}
//NIE MA DESTRUKTORA BO NIE ALOKUJE ZADNYCH DANYCH !!!
void show(){
cout<<this->wrt<<endl;
}
private:
Node* next;
int wrt;
};
class List{
public:
List(int wrt){
this->root = new Node(NULL, wrt);
}
List(const List& list)
{
// jesli pusty kopiujemy
if (list.root == NULL)
{
this->root = NULL;
return;
}
//tworzenie nowego korzenia
this->root = new Node(NULL, list.root->wrt);
Node* list_currentNode = list.root;
Node* this_currentNode = this->root;
while (list_currentNode->next != NULL)
{
// tworzenie nastepnika
Node* newNode = new Node(NULL, list_currentNode->next->wrt);
this_currentNode->next = newNode;
this_currentNode = this_currentNode->next;
list_currentNode = list_currentNode->next;
}
}
void add(int wrt){
Node* node = new Node(NULL, wrt);
Node* el = this->root;
while(el->next != NULL){
//el->show();
el = el->next;
}
el->next = node;
}
void remove(int index){
Node* el = this->root;
if(index == 0){
this->root = el->next;
// delete el;
}
else{
int i = 0;
while(el != NULL && i < index - 1){
el = el->next;
i++;
}
if(el!=NULL){
Node* toRem = el->next;
Node* newNext = toRem->next;
el->next = newNext;
// delete toRem;
}
}
}
void show(){
Node* el = this->root;
while(el != NULL){
el->show();
el = el->next;
}
}
~List(){
Node* currentNode = this->root;
while (currentNode != NULL)
{
Node* nextNode = currentNode->next;
delete currentNode;
currentNode = nextNode;
}
}
private:
Node* root;
};
int main(){
List* l = new List(10);
l->add(12); l->add(13);
l->show();
cout<<endl;
List* lala = new List(*l);
lala->show();
cout<<endl;
lala->add(4);
cout<<"lala before remove"<<endl;
lala->show();
lala->remove(0);
cout<<"l before delete"<<endl;
l->show();
cout<<"lala before delete"<<endl;
lala->show();
delete l;
cout<<"l after"<<endl;
l->show();
cout<<"lala after delete"<<endl;
lala->show();
return 0;
}
First Part
Following three statements are causing infinite loop..
l->~List();
cout<<"l after"<<endl;
l->show();
Because your destructor ~List() misses an important statement, which is...
this->root = NULL;
Which is the main reason for infinite loop. So here your full destructors goes..
~List()
{
Node* currentNode = this->root;
while (currentNode != NULL)
{
Node* nextNode = currentNode->next;
delete currentNode;
currentNode = nextNode;
}
this->root = NULL;
}
Second Part
Now as you have update above three lines into following...
delete l;
cout<<"l after"<<endl;
l->show; // We should never write this line in general practice..
And considering that you're using above ~List() function. The reason for still program goes into an infinite loop is that delete l will de-allocate memory assigned to l. And you call l->show() (and as l is still pointing to an accessible linear address), so now this->root is pointing to some garbage location and thats why until it finds luckily while(el != NULL) condition NULL, it will stay in infinite-loop.